Giardiasis

Giardiasis is a diarrheal illness caused by Giardia lamblia, a microscopic parasite that lives in people and animals. Infected people and animals pass Giardia cysts in their stool. These cysts can survive in the environment in water and food and on surfaces and objects.

Symptoms include diarrhea, abdominal cramps, nausea, bloating, gas, fatigue, weight loss, and dehydration. Symptoms generally begin one to two weeks after being infected. In otherwise healthy persons, symptoms usually last two to six weeks, but occasionally last longer. Some infected people do not develop any symptoms. Persons at increased risk for giardiasis include children and staff in day care centers, international travelers, hikers, campers, swimmers, and others who drink or accidentally swallow water from contaminated sources. Persons who have unprotected anal sex are also at increased risk of contracting giardiasis.

Giardia may be found in soil, food, water, or on surfaces that have been contaminated with feces from infected people or animals. People become infected after accidentally swallowing Giardia cysts. For example, hikers, backpackers, and campers sometimes get giardiasis by drinking from lakes, streams, and ponds that have been contaminated by animals. Giardiasis can also be spread from person-to-person, such as in day care centers that care for children in diapers.

Giardiasis is usually diagnosed by using a microscope to identify Giardia cysts in a stool sample. Some people recover without treatment, but persistent infections may require antibiotics. There are several prescription drugs available to treat Giardia. People with severe diarrhea should drink plenty of fluids, especially young children and pregnant women who may be more susceptible to dehydration.

How can giardiasis be prevented?

Wash your hands with soap and water after using the toilet, changing diapers, and before eating or preparing food.

Avoid drinking untreated water from shallow wells, lakes, streams, and ponds. If unable to avoid drinking or using water that might be contaminated, purify water by boiling, filtration, or iodine treatments.

Carefully dispose of disposable diaper and sewage wastes so as not to contaminate surface or groundwater.

Avoid fecal exposure during sex.

Anyone with giardiasis should avoid swimming pools. Giardia cysts are resistant to chlorine levels used in swimming pools and are passed in the stools of infected people for several weeks, even after they no longer have symptoms.

Day care centers should teach the importance of handwashing to children and staff.

People with diarrhea need to be excluded from group settings where they may present a risk to others such as daycare centers and schools. Some health departments may require food handlers and childcare workers who have giardiasis to test negative for Giardia before returning to work. People who are not in high-risk settings may return to their routine activities when they have recovered, however, they should carefully wash their hands after using the toilet.